Artificial marble used as architectural materials may be classified into two groups according to the base resin material. One group represents acrylic artificial marble, and the other group represents unsaturated polyester artificial marble. Acrylic artificial marble has found wide utilization as a material for kitchen countertops, wash basins, dressing tables, bathtubs, various table surfaces, wall materials, interior articles, and the like, because it has an excellent appearance, high-gloss texture, and good weather resistance.
Various methods have been proposed for preparing an artificial marble having an amorphous pattern, such as mixing various synthetic materials having different colors and pouring the mixed composition in the liquid phase into a molding cell. Such methods, however, can provide only an artificial marble with a two-dimensional image because the parts forming the pattern of the artificial marble are not transparent.
Transparent resins such as acrylic, styrenic, and carbonate resins can be used in order to provide transparency to parts forming a pattern in the artificial marble. However, the transparent resin forming pattern parts in the artificial marble can shrink more than a matrix resin including lots of fillers surrounding the pattern parts during the hardening (curing) process. This can result in cracking at the interface of the pattern part and the matrix, which is also referred to as a concave phenomenon.
Further, the pattern part may migrate to an upper portion of the artificial marble in the hardening process because of the excessive difference between the specific gravity of the matrix resin and the pattern part. Because either surface of the artificial marble can be used as the exposed surface in a product including the artificial marble, the migration of the pattern part can be problematic.
Inorganic fillers such as aluminum hydrate, barium sulfate, silica and the like can be introduced in order to increase the specific gravity at the level of matrix. This, however, can significantly decrease transparency of the pattern part.
It can also be difficult to control the refractive ratio of inorganic filler to control transparency because the size of the inorganic filler used in artificial marble may also affect transparency.